The invention relates to a fire-fighting installation comprising a drive source for feeding medium into at least one spray head of the fire-fighting installation, said at least one spray head releasing by impact of heat, the drive source comprising a pump unit for feeding liquid into said at least one spray head through a supply line, a portion of the supply line restricted to the spray head being filled with gas provided with a standby pressure, a gas source for maintaining the standby pressure of the supply line and a sensor arranged to provide a signal for starting the pump unit in response to a change occurring in the state of the medium in the supply line.
The invention also relates to a drive source of a fire-fighting installation comprising a pump unit for feeding liquid into the fire fighting installation.
What are known as preaction fire extinguishing installations comprise a drive source like the one mentioned above. In such a case, the fire extinguishing installation comprises a sensor in the form of a pressure sensor for starting the pump unit. The pressure sensor reacts to the decline of the gas pressure in the supply line and starts the pump unit for feeding liquid into the sprinklers of the fire extinguishing installation. In a typical sprinkler system the dimensioning flows of liquid are extensive, whereby the pipe volumes and the discharge openings of the liquid are also large. In a dry (mounted) system the gas volumes are therefore also large and when the system releases, the gas discharges and correspondingly the pressure drops rapidly. The pressure sensor rapidly starts the pump unit and liquid flows from the sprinklers during an acceptable time, generally 30 seconds, from the release. This is important in order to be able to efficiently and rapidly extinguish fires. Dry-mountable fire extinguishing installations are also previously known in the art that are dimensioned—for different reasons—in such a manner that the liquid starts flowing 60 to 90 seconds from releasing the spray head. Such fire extinguishing installations are not suitable to be mounted for all purposes owing to the reduced speed thereof.
Prior art fire extinguishing installations and the drive sources thereof operate satisfactorily when the pressure is rapidly reduced in the supply line as a result of the extensive flow started in the supply line. In fire extinguishing installations the flow generally becomes large, when they comprise conventional spray heads conveying a rain-like or liquid jet flow, in other words spray heads provided with nozzles comprising large openings. Then again, particularly mist-type fire extinguishing installations including spray heads conveying a mist-like flow and being able to efficiently extinguish/fight fires by spraying mist use a minor amount of liquid. In these installations, the flow is much smaller and the pressure is not reduced rapidly enough in the supply line in order for the pressure sensor to react to the reduction of pressure in an acceptable time.